PP51B-2286
Foraminifer- and diatom-based paleoceanographic study of Holocene sediments from the Sabrina Coast, East Antarctica

Friday, 18 December 2015
Poster Hall (Moscone South)
Kara Jayne Vadman1, Amelia Shevenell2, Amy Leventer3, Eugene W Domack2, Bruce A Huber4, Alejandro Hector Orsi5 and Sean P S Gulick6, (1)University of South Florida Tampa, Tampa, FL, United States, (2)University of South Florida, Tampa, FL, United States, (3)Colgate University, Geology, Hamilton, NY, United States, (4)Lamont -Doherty Earth Observatory, Palisades, NY, United States, (5)Texas A & M University, College Station, TX, United States, (6)University of Texas at Austin, Institute for Geophysics, Austin, TX, United States
Abstract:
Cruise NBP14-02 conducted the first interdisciplinary oceanographic survey of the continental shelf adjacent to the Totten Glacier-Moscow University Ice Shelf system on the Sabrina Coast, East Antarctica. Hydrographic data indicate that this system is presently influenced by subsurface (>350 m) intrusion of relatively warm (>0°C) modified Circumpolar Deep Water (mCDW) via a cross-shelf trough. To assess the late Quaternary influence of mCDW, we collected marine sediment cores at two locations, each of which recovered a complete 10-13 m sequence of glacial diamict and Holocene laminated diatom ooze/mud. Chronology is constrained by 210Pb and species-specific foraminifer-based AMS 14C dates.

Foraminifer CaCO3 is most abundant in surface sediments (0-0.2 mcd) and from 1.5 to 5 mcd. Planktic foraminifer, Neogloboquadrina pachyderma(s), dominates surface sediments and diatom muds downcore, but is less abundant in diatom oozes. Benthic foraminifer species, Bulimina aculeata, which prefers hemipelagic environments and bottom waters >0°C, dominates the living benthic assemblage. The fossil benthic assemblage is characterized by Trifarina angulosa, associated with oxygenated bottom waters and strong bottom currents, suggesting that this assemblage may record past changes in the shoreward flow of ocean currents and the location of oceanic frontal zones. T. angulosa presence in oozes of mat-forming diatom species associated with oceanic fronts, supports this interpretation.

Modern benthic and planktic δ18O suggest a well-mixed water column. Below 1.5 mcd, foraminifer isotopes and diatom assemblages indicate surface stratification and increased biogenic productivity, suggesting that modern environmental conditions, including mCDW inflow, existed episodically during the Holocene. Paired T. angulosa δ18O and Mg/Ca analyses will provide additional information on past mCDW influence on this climatically sensitive region at the outlet of the extensive (287,000 km2) Aurora Subglacial Basin, which holds a 2-4.5 km thick volume of ice equivalent to >5 m of eustatic sea level rise.

<< Previous Abstract | Next Abstract >>